Electric conductor



Oct. 27, 1931. o. 1A, FREDERIC-KSON ELECTRIC CONDUCTOR Filed Sept. 19, 1928 2 Sheets-Sheet l HV1/ENT ma 62. MMM

. ATTORNEY Oct. 27,?1931.

o. A. FREDERICKSON 1,828,772

ELECTRIC CONDUCTOR Filed sept. 19, 192e 2 sheets-sheer 2 111.9 /NVENTOR MQW E316 f BY,

A TTR/VEY Patented 27, i931 g UNITED STATES OTTO A. FBEDEBICKSON, OP WmBSFIELD, CONNECTICUT, ASSIGNOB TO NATIONAL' ELECTRIC PRODUCTS CORPORATION, F PITTSBURGH, PENNSYLVANIA, .A CORPORA- TION OF DELAWARE ELECTRIC CONDUCTOR Application led September 19, 1928. Serial No. 306,976.

This invention relates to insulated electric conductors, and more particularly to a protecting covering of insulating material that is well adapted for use either as an outer protecting jacket for a conductor or as a protecting covering over which the outer metallic sheath of an armored cable or conductor ma be applied.

he present application is being iled for the purpose of embodying in a single patent the subject-matter of application, Serial No. 212,187, filed August 11, 1927 and the subject-matter that has been divided from Patent 1,687,013 dated October 9, V1928.

The present protecting covering is preferably made of paper, and while paper has been used heretofore as a protectlng wrapper for electric conductors, in the form of at strips and also as hard twisted paper isfactory due to the fact that small cracks or crevices frequently exist between the adjacent coils, and also to the fact that when the electric conductor having-the paper covering g formed thereon as heretofore is bent, protant feature of the present invention resides in a paper covering for electric conductors formed of one or more relatively soft thick paper strands wrapped about the conductors so that the edges of t-he adjacent coilsoverlap to form a smooth, durable jacket that is from cracks or crevices between the adjacent coils of paper.- The construction of the paper strands is preferably such Y that the lstrands will flatten out somewhat as they are wound tightly about the conductor and form tapered opposite edges adapted to overlap the adjacent coils to close the cracks or crevices therebetween, and as a result o f this construction the covered conductor may be bent to a pronounced degree without causing gaps to form between the coils at the outer surface strands or cords, it has not been entirely sat-4 of the bent conductor or the piling up of the coils at the inner curved surface of the bend. The relatively soft thick paper strands employed to' form the protecting covering of the present invention are preferably formed of thin paper that is crumpled or creased longitudinalljLto produce a rounded, compressible strand that will conform readily to the surface about which it is Wrapped and as a result the overlapping tapered edges of the adjacent coils will sink one into the other to form smooth tight joints between them, which, as above stated, will not open even when the covered conductor is bent at a pronounced angle. The tight j'oints thus formed impart to the paper covering a continuous unbroken surface which affords excellent mechanical and electrical'protection to the underlying conductor.

As above indicated, he present protecting covering is not lonly well adapted for use as an outer protecting covering, but also constitutes an excellent wrapper over which the metallic sheath or jacket of a flexible armored conductor may be applied. In the formation of these metallic sheaths, metal slivers or sharp edges are frequently produced which are likely to injure the under,- lying insulating material and in some cases penetrate through the insulation to short circuit the conductors. When the paper covering forming the subject-matter of the present invention is provided under the metallic jacket it is practically impossible for the `sli vers to penetrate through this paper covermg. 4

Furthermore, since the paper covering is formed of soft compressible aper strands, the paper wrapper will be su ciently soft to constitute a cushionabout'the conductor and into which the coils of the armored sheath may sink to form a locking engagement between the metal jacket and lunderlying insulating cover to prevent sliding Amovement therebetween. In this manner the sliding movement between the covered conductors and armored jacket, which hasbeen a source of annoyance heretofore, is entirely prevented.

Still another vfeature of the present invenloo tion resides in the fact that when a protecting covering constructed in accordance with the present invention is placed about a conductor or conductors within an armored outer jacket, such paper covering can be readily drawn out from the interior o an end portion of the armored cable for the purpose of forming a clearance space, in which a sleeve to be described may be inserted.

The above and other features of the invention will be best understood from the following description when read in connection with the accompanying drawings illustrating good practical forms of the invention.

In' the drawings:

Fig. 1 is a perspective view of a .soft rounded strand of paper employed in forming the protecting covering of the present invention;

Fig. 2 is a perspective view of a conductor having a protecting covering formed in accordance with the present invention;

Fig. 3 is a perspective view of a modiiied construction Fig. 4 on an enlarged scale is a side view of Fig. 2 with parts in section;

Fig. 5 is a sectional view through a bent portion of the conductor;

Fig. 6 is a side view with parts 'in section of a modified construction in which the present invention is embodied in' an armored cable; j

Fig. 7 is an enlarged vertical sectional view through the conductor of Fig. 6;-

Fig. 8 is a perspective view of a sleeve to be described; and

Fig. 9 is a sectional view showing the sleeve of Fig. 8 inserted in the end of the armored cable of Fig. 6.

The protecting covering of the present invention may be formed by wrapping one or more paper strands about an insulated conductor, or such strand or strands may be wrapped about a plurality of insulated conductors, as will be apparent from the various embodiments of the invention shown in the drawings, and the protecting covering may be used as an outer covering or as a cushioning inner covering over which an outer jacket of any desired construction may be placed.

The electric conductor 10 may be formed of a single strand of wire or a number of line twisted strands as is usual, and about the conductor 10 is applied a jacket l1 formed of rubber or other suitable insulating material. Over the jacket 11 may be provided a covering 12 which is braided or otherwise constructed, and the protecting covering forming the subject-matter of the present invention may be applied over the braid 12, as

shown in Figs. 2, 3 and 5, or it may be applied directly to the jacket 11, as s hown in the modified construction of Fig. 3. t

The paper covering may be formed of a single strand of paper v13 that is wound spirally about the conductor, as shown in Fig. 3, or it may be formed of a plurality of strands, as 'will be apparent from Fig. 2, in which four strands of paper 13 arewound spirally about the conductor. The paper strand or strands 13 are preferably formed of a thin soft flexible sheet of paper 14 that is crumpled longitudinally into a soft rounded strand as shown. The strand may beuntwisted, as shown, or it may have a few twists to help in the formation of the strand, but in either case it is important that the strand 13 be so formed that it will be soft and compressible when applied to the conductor, so that it will spread out when wound tightly about the covered conductor into a somewhat elliptical shape in cross-section and have tatight joint between them. As a result of this construction, a smooth continuous paper covering is formed about the conductor and the cracks or joints between adjacent coils are so formed that they-will not open even when the covered conductor is bent, as shown in Fig. 5. The bending of the cable will, of course, crowd the coils 15 together somewhat at the inside of the bend and spread them apart at the outside of the bend, but the overlapping construction 16 will prevent the formation of cracks or crevices at the outside of the bend.

It may be desirable to adhesively secure the coils 15 to the jacket they surround and this may be done by applying any suitable ad.

hesive 17, such as stearln pitch, for example, to the surface about which the paper 13 is wound. The adhesive'will firmly secure the coils-in place and will prevent the strands 13 from becoming accidentally unwrapped, and if the adhesive 17 is applied in a relatively thin layer it will not enter the crack 16 to a suflicient extent to prevent a relative movement between these overlapping edges when the cable is bent.

The outer surface of the paper covering may also be treated with pitch or the like 17 to prfotect the covering and render it waterroo p The crumpled paper strand 13 preferably has the rounded construction shown in Fig. 1 before it is wound about the covered conductor, but due to the soft com ressible nature of this crumpled strand it wi l readily flatten out as'it is wrapped about the insulated conductor, as above pointed out, to produce the desired overlapping effect of the tapered sesam edges of the adjacent coils 15, and these overlapping edges fit together so snugly that an extremely t1 ht joint is formed between them, thus producing a protecting covering having a smooth outer surface that is free from cracks and interstices while it is suiciently flexible to permit the conductor to be freely bent without causin thecracks between the coils to open. Furt ermore, this soft paper covering forms a compressible cushion which is desirable when the coverin 15 is provided with a surrounding jacket o insulatin material, as it will re ieve such outer insu ating jacket from excessive internal pressure when the conductor is bent or subjected to a crushing pressure.

n the modified construction shown in Figs. 6, 7 and 9, two covered conductors, which may be similar to the covered conductor 12 of Fig. 2, are enclosed in a protecting coverin 15 formed of the paper strands 13 wrapped a out the conductors with their edges in overlapping relation, as above described, and about the covered electric conductors thus formed is provided a flexible metallic sheath or jacket 18 which may be of usual or any preferred construction em loyed in the manufacture of flexible armore cables.

The stri of metal forming the armore jacket '18 1s preferably wound suiciently tight about the covering 15 to cause the metal coils to sink slightl into the surface of the cushioning materia 15 to thereby lock the covered conductors against sliding movement within the armored jacket, with the result l that chafing of the covering caused by a relachafing or otherwise injurin .the underlyingent sleeve 20 is tive movement of the insulated covering'and ,armored jacket is prevented.

The metal strip which is Wound about the covered conductors to form the metallic jacket 18 may have sharp edges or slivers 19 that are accidentally formed, and it is found that when the insulated conductors are provided with a braided o'r woven covering these metal slivers 19 may enter the interstices of the braid of woven fabric and short-circuit the conductors. When insulated conductors are provided with a protecting covering constructed in accordance with the present invention it is practically impossible for these slivers 19 to penetrate through the surface of the paper covering 15 or to enter the tightlyclosed joints 16 between the adjacent co1 s.

As ointed out in the above-mentioned aplcation Serial No. 238,356, it is desirable to lnsert a sleeve in the end 'of the metallic 'acket 18 to prevent the sharp edges that may formed in cutting off the jacket from insulation 15. The split resi therefore provided for this urpose and may be inserte in the end portion of the jacket 18 b merely compressing the sleeve between the ngers while it is inserted in place, but before this is done it is necessary to form a -ductor, 'a protecting coverin metallic jacket to receive the sleeve. Such clearance space is readily formed when the covering wlthin' the metallic sheath is constructed in accordance with the present inclearance space within the end portion of the vention, since all that is necessary is to unwind from about the covered conductor 12 one'or more coils 15 within the end portion of the metallic sheath, as will be ap arent from Fig. 6, whereu on, the unwoun coils may be broken of wlthin the sheath 18, due to the com aratively low tensile strength of the crump ed paper strands 13, to form the desired clearance space in which the sleeve 20 may be inserted as will be a parent from Fig.

9, and it should be noted t at this clearance space is formed without necessitating the use of any cutting tool that might injure thepunderlying insulation. j

It will be apparent from the foregoing that a paper covering constructed in accordance with the present invention is tough and durable, affords excellent mechanical and electrical protection, readily accommodates itself to the bending of the conductor, may be produced at low cost, and possesses many other desirable features as above pointed out.

What is claimed is:

1. An armored electric conductor comprising in combination, an insulated conductor, a protecting coverin wound about the insulated conductor an formed of a soft, crumpled, readily compressible strand of paper wound about the insulated conductor which has'tapered edges that extend into overlapping relation with the adjacent Icoils, and an armored outer sheath formed of metal Wound about the soft paperlcovcr# ing in engagement therewith so that the coils of the armor may sink into the soft paper covering sufliciently to prevent sliding movement of the conductor within the armored sheath. l

2. An armored electric conductor, comprising in combination, an insulated conductor, a protecting coverin wound about the insulated conductor an formed of a soft readil compressible paper strand that assumes a attened shape wit tapered edges when wound about the conductor and havlng the adjacent edges disposed so that the' taf pered edge of one coil overlaps the tapered edge of the next coil to form joints between the coilsthat are practically impenetrable to metal slivers produced informing the armor, land an armored outer sheath formed of. a metal strip wound spirally about the insulated Wire over said protecting covering.

3. An armored electric conductor comprising in combination, van insulated conwound about the insulated conductoran formed of a readily compressible' paper strand that assumes a flattened shape with tapered edges when'wound about the conductor and having izo- 4 Lezama the adjacent edges disposed so that the tapered edge of one coil overlaps the tapered edge of the next coil to form joints between the coils that are practically impenetrable to metal slivers produced in forming the armor, and an armored outer sheath formed of a metal strip wound spirally about the insulated Wire over said protecting covering with its coils interlocked with the cushioning paper covering and preventing sliding movement of the conductor Within the armored sheath.

4. An armored electric conductor comprising in combination, an insulated conductor, a metallic sheath wound about and surrounding said insulated conductor, a protecting covering wound about said insulated conductor within the metallic sheath and formed of a soft crumpled strand of paper that assumes a flattened shape with tapered edges when wound snugly about the covered conductor and having the adjacent coils disposed with a tapered edge of one coil lying in overlapping relation with a tapered edge of the next coil and disposed so that one or more coils may be unwound from the insulated conductor Within the metallic sheath and then broken ofi' therein to form a clearance space within the end portion of the o sheath.

5. A s'an article of manufacture, an insulated electric conductor having a protecting' covering wound spirally about the conductor and formed of a homogenous thin soft paper strip crimped or crumpled longitudinally into an untwisted covering element that is laterally pliable and assumes a flattened or oval shape in cross-section with tapered edges when Wound spirally about the conductor 40 and having the adjacent coils ofthe crumpled paper covering element disposed with the tapered edge of one coil overlapping the tapered edges of the next coil and each coil being sufficiently pliable to conform snuglyl to the edge portion of the coil it overlaps.

In testimony whereof, I have signed my name to this specification.

.OTTO A. FREDERICKSON. 

